Simple Network: And the Default Gateway is?

I know enough networking to be dangerous :-), but i just cannot get my head round how to configure a default gateway.

I have a small network consisting of a dumb 8 port switch connected to 2*Laptops and a printer, plus a wireless bridge in PTMP mode with 10 further stations. It all works fine.

NB this is a standard alone network without any connection to the Internet or other network.

But now i want to add a router so that i can add some extra functionality. The first big problem i have is what do i specify as my default gateway.

If i setup my router so that
Port-1 = 192.168.0.5
Port-2 = 192.168.0.6
Port-3 = 192.168.0.7

and the rest of my network, has addresses between .0.10 and .0.99

what do i set the default gateway too?
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Gerald ConnollyAsked:
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Don JohnstonInstructorCommented:
If i setup my router so that
Port-1 = 192.168.0.5
Port-2 = 192.168.0.6
Port-3 = 192.168.0.7

You won't be able to do that.  A router can only have one connection to a network.

So if you have a 4-port router, every port would have to connect to a different network. i.e.:

Port-1 = 192.168.1.1
Port-2 = 192.168.2.1
Port-3 = 192.168.3.1
Port-3 = 192.168.4.1

If you want to connect your network to the internet, you would use a 2-port router. One port would be connected to your LAN (192.168.0.1) and the other port would connect to the internet (using a public address).  The default gateway for all of your hosts would be 192.168.0.1.
HaroldNetwork EngineerCommented:
In a network and no internet, its your GW to reach another network. If R1's(router) network needs to reach R2's network, everything needing to reach R2s network will use Rs1 IP, as their GW. (basically)
Or reaching the internet, your routers IP is the GW for your network to reach the net. (can be a little simpler)  This is most of the time configured in a DHCP server, but can be static.
HTH
Ken BooneNetwork ConsultantCommented:
So you have a flat network - 192.168.0.x

You need a router to be used as a default gateway in order to reach other networks that you are not directly on.  So if you added another dumb switch and set up machines on that dumb switch with say 192.168.100.x addresses that would be another network.  

Then you would use a router to connect those two networks.  The router would have port 1 on the 192.168.0.x network and port 2 on the 192.168.100.x network.

So lets say port 1 is 192.168.0.1 and port 2 is 192.168.100.1.

So for all 192.168.0.x devices you would use 192.168.0.1 as their default gateway and for all 192.168.100.x devices you would use 192.168.100.x as their default gateway.

That is how that works.

Your scenario is not valid as a router can only have 1 ip address per subnet configured.  You have 3 so that won't work.

What exactly are you trying to accomplish with the router?

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Gerald ConnollyAuthor Commented:
Basically one of my laptops is the key to all of this (192.168.0.20)

Its on a dumb switch with 2 other devices that both connect to the master and a PTMP wireless bridge that connects to 5 other locations that all have addresses in the .0.xxx range.

But everything is geared so that every end node can connect to the master.

Now i want to add the capability of a lot more devices, but want to keep them on a different subnet.

NB have i said that this network is standalone, and will NOT be connecting to the Internet, certainly not in the short-term.

So if i set Port-1 of my router to be 192.168.0.1 and connect that to my existing network, and set Port-2 to 192.168.100.1

what should i set my GW to? so that devices in the .100.xxx range can connect to my master machine.
Ken BooneNetwork ConsultantCommented:
ok so that means that devices in the 100.x range will use the 192.168.100.1 address as their default gateway.  Likewise you will need to set the devices in the 0.x range to use 192.168.0.1 as their default gateway so they can talk back to the devices on the 100.x range.
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